Calculations of the evolution of cosmological perturbations generally involve solution of a large number of coupled differential equations to describe the evolution of the multipole moments of the distribution of photon intensities and polarization. However, this “Boltzmann hierarchy” communicates with the rest of the system of equations for the other perturbation variables only through the photon-intensity quadrupole moment. Here I develop an alternative formulation wherein this photon-intensity quadrupole is obtained via solution of two coupled integral equations—one for the intensity quadrupole and another for the linear-polarization quadrupole—rather than the full Boltzmann hierarchy. This alternative method of calculation provides some physical insight and a cross-check for the traditional approach. I describe a simple and efficient iterative numerical solution that converges fairly quickly. I surmise that this may allow current state-of-the-art cosmological-perturbation codes to be accelerated.

The canonical velocity-dependent one-scale (VOS) model for cosmic string evolution must be calibrated using high resolution numerical simulations, We exploit our state of the art graphics processing unit accelerated implementation of the evolution of local Abelian-Higgs string networks to provide a detailed and statistically robust calibration of the VOS model. We rely on the largest set of high resolution simulations carried out to date, with a wide range of cosmological expansion rates, and explore the impact of key numerical parameters, including the dynamic range (comparing box sizes from ${1024}^3$ to ${4096}^3$), the lattice spacing, and the choice of numerical estimators for the string velocity. We explore the sensitivity of the VOS model parameters to these numerical parameters, with a particular emphasis on the observationally crucial loop chopping efficiency, and also identify key differences between the equation of state and conjugate momentum estimators for the string velocities, showing that the latter one is more reliable for fast expansion rates (while in Minkowski space the opposite has been previously shown). Finally, we briefly illustrate how our results impact observational constraints on cosmic strings.

In prerecombination resolutions of the Hubble tension, such as early dark energy, new physics before recombination shifts the values of relevant cosmological parameters so that the models can fit with cosmic microwave background and baryon acoustic oscillations observations as well as LambdaCDM does. In this paper, we clarify how the parameter shifts are related with $\delta H_0$, particularly we find the shift of primordial scalar spectral index scales as $\delta n_s\simeq 0.4\frac{\delta H_0}{H_0}$ by performing the Monte Carlo Markov chain analysis with the $\mathrm{Planck}2018+\mathrm{BAO}+\mathrm{Pantheon}+\mathrm{R}19+\mathrm{Keck}$ Array/BICEP dataset. A novel point of our result is that if the current $H_0$ measured locally is correct, complete resolution of the Hubble tension seems to be pointing to a scale invariant Harrison-Zeldovich spectrum, i.e., $n_s=1$ for $H_0\sim 73\mathrm{km}/\mathrm{s}/\mathrm{Mpc}$.

We study the observational predictions of the phenomenological anti-de Sitter (AdS)/QCD inspired model, in which the inflaton field emerges in a four-dimensional strongly coupled gauge theory, in which the chiral symmetry breaking occurs through the formation of the quark condensate. Based on a top-down approach of AdS/QCD, using a D7-brane in the background of $N_c$ D3-branes, it has already been shown that chiral symmetry breaking in a magnetic field through the generation of the Higgs vacuum expectation value could be a second-order phase transition, although it was doubted that this scenario could lead to enough inflation. Using an iterative method, we consistently solve for the time-dependent parameters, including the embedding function of the D7-brane and the Hubble parameter of the expanding background. We show that with $N_c\sim {10}^7$ and $g_{\mathrm{UV}}\sim \mathrm{few}\times 0.1$, the predictions of the inflationary model are consistent with the most stringent constraints placed on the inflationary models by Planck 2018. Although the model is capable of producing a large amount of gravitational waves, $r\simeq 0.01$, the displacement of the canonical mass dimension-1 scalar field remains below the Planck mass, in violation of the Lyth bound.

In this article, we reevaluate supernovae (SN) constraints on the diffusion time of neutrinos for a family of extensions of the Standard Model that incorporate new light scalar and vector mediators. We compute the neutrino mean free path, taking into account medium effects in the neutrino-nucleon scattering cross section, and a radial dependence of the density, energy, and temperature inside the proto-neutron star to determine the coupling strengths compatible with SN1987A constraints on the time duration signal of diffusing neutrinos. We show that medium effects can induce an order of magnitude enhancement in the neutrino mean free path with respect to the vacuum calculation. The increase is more significant when new physics terms dominate over the Standard Model contribution (that is, for small mediator mass and large couplings). Finally, we interpret these results as bounds on the parameter space of a vector $U(1{)}_{B-L}$ model and scalar lepton number conserving and lepton number violating scenarios, improving on previous results in the literature where medium effects were ignored. We show that SN constraints on the neutrino diffusion time lie within regions of the parameter space that are already ruled out by other experimental constraints. We also comment on potential limits due to changes in the SN equation of state or right-handed neutrino free-streaming, but argue that detailed numerical simulations are needed to improve the reliability of these limits.

The Large High Altitude Air Shower Observatory (LHAASO) is one of the most sensitive gamma-ray detector arrays currently operating at TeV and PeV energies. Recently the LHAASO experiment detected ultra-high-energy (UHE; $E_{\gamma }\gtrsim 100\mathrm{TeV}$) photon emissions up to 1.4 PeV from twelve astrophysical gamma-ray sources. We point out that the detection of cosmic photons at such energies can constrain the photon self-decay motivated by superluminal Lorentz symmetry violation (LV) to a higher level, thus can put strong constraints to certain LV frameworks. Meanwhile, we suggest that the current observation of the PeV-scale photon with LHAASO may provide hints to permit a subluminal type of Lorentz violation in the proximity of the Planckian regime, and may be compatible with the light speed variation at the scale of $3.6\times {10}^{17}\mathrm{GeV}$ recently suggested from gamma-ray burst (GRB) time delays. We further propose detecting PeV photons coming from extragalactic sources with future experiments, based on LV-induced threshold anomalies of $e^{+}{e}^{-}$ pair-production, as a crucial test of subluminal Lorentz violation. We comment that these observations are consistent with a D-brane/string-inspired quantum-gravity framework, the space-time foam model.

We determine the ability of Cosmic Explorer, a proposed third-generation gravitational-wave observatory, to detect eccentric binary neutron stars and to measure their eccentricity. We find that for a matched-filter search, template banks constructed using binaries in quasicircular orbits are effectual for eccentric neutron star binaries with $e_7\le 0.004$ ($e_7\le 0.003$) for CE1 (CE2), where $e_7$ is the binary’s eccentricity at a gravitational-wave frequency of 7 Hz. We show that stochastic template placement can be used to construct a matched-filter search for binaries with larger eccentricities and construct an effectual template bank for binaries with $e_7\le 0.05$. We show that the computational cost of both the search for binaries in quasicircular orbits and eccentric orbits is not significantly larger for Cosmic Explorer than for Advanced LIGO and is accessible with present-day computational resources. We investigate Cosmic Explorer’s ability to distinguish between circular and eccentric binaries. We estimate that for a binary with a signal-to-noise ratio of 20 (800), Cosmic Explorer can distinguish between a circular binary and a binary with eccentricity $e_7\gtrsim {10}^{-2}$ (${10}^{-3}$) at 90% confidence.

In this paper, we propose a generalized natural inflation model to study axionlike particle (ALP) inflation and dark matter. The model contains two additional parameters $(n_1,n_2)$ in comparison with the natural inflation model. The $n_1$ builds the connection with other ALP inflation models, and the $n_2$ controls the inflaton mass. After considering the cosmic microwave background and other cosmological observation limits, the model can realize small-field inflation with a wide mass range, and the axionlike particle inflaton considered here can serve as the dark matter candidate for certain parameter spaces.

The success of the multimessenger astronomy relies on gravitational-wave observatories like LIGO and Virgo to provide prompt warning of merger events involving neutron stars (including both binary neutron stars and neutron-star-black-hole binaries), which further depends critically on the low-frequency sensitivity of LIGO as a typical binary neutron star stays in this band for minutes. However, the current sub-60 Hz sensitivity of LIGO has not yet reached its design target and the excess noise can be more than an order of magnitude below 20 Hz. It is limited by nonlinearly coupled noises from auxiliary control loops which are also nonstationary, posing challenges to realistic early warning pipelines. Nevertheless, machine-learning-based neural networks provide ways to simultaneously improve the low-frequency sensitivity and mitigate its nonstationarity, and detect the real-time gravitational-wave signal with a very short computational time. We propose to achieve this by inputting both the main gravitational-wave readout and key auxiliary witnesses to a compound neural network. Using simulated data with characteristic representing the real LIGO detectors, our machine-learning-based neural networks can reduce nonlinearly coupled noise by about a factor of 5 and allows a typical binary neutron star (neutron-star black hole) to be detected 100 s (10 s) before the merger at a distance of 40 Mpc (160 Mpc). If one can further reduce the noise to the fundamental limit, our neural networks can achieve detection out to a distance of 80 and 240 Mpc for binary neutron stars and neutron-star-black-hole binaries, respectively. It thus demonstrates that utilizing machine-learning-based neural networks is a promising direction for the timely detection of the coalescence of electromagnetically bright LIGO/Virgo sources.

We investigate precision observables sensitive to custodial-symmetric/-violating UV physics beyond the Standard Model. We use the Standard Model effective field theory (SMEFT) framework which in general includes nonoblique corrections that require a generalization of the Peskin-Takeuchi $T$ parameter to unambiguously detect custodial symmetry/violation. We take a first step towards constructing a SMEFT reparametrization-invariant replacement, which we call $𝒯$, valid at least for tree-level custodial-violating contributions. We utilize a new custodial basis of $\nu \mathrm{SMEFT}$ (SMEFT augmented by right-handed neutrinos) which explicitly identifies the global $SU(2{)}_R$ symmetries of the Higgs and fermion sectors, which in turn permits easy identification of higher-dimensional operators that are custodial preserving or violating. We carefully consider equation-of-motion redundancies that cause custodial-symmetric operators in one basis to be equivalent to a set of custodial-symmetric and/or -violating operators in another basis. Utilizing known results about tree/loop operator generation, we demonstrate that the basis-dependent appearance of custodial-violating operators does not invalidate our $𝒯$ parameter at tree level. We illustrate our results with several UV theory examples, demonstrating that $𝒯$ faithfully identifies custodial symmetry violation, while $T$ can fail.

In this work, the $p-p(\overline{p})$ Drell-Yan lepton pair production (DY) differential cross sections at hadron colliders, such as LHC and TEVATRON, are studied in the $k_t$-factorization framework. In order to take into account the transverse momenta of incoming partons, we use the unintegrated parton distribution functions of Kimber et al. (KMR) and Martin et al. (MRW) in the leading order (LO), and next-to-leading-order (NLO) levels with the input MMHT2014 PDF libraries. Based on the different off shell partonic matrix elements, we analyze the behaviors of DY differential cross sections with respect to the invariant mass, the transverse momentum and the rapidity as well as the specific angular correlation between the produced leptons. The numerical results are compared with the experimental data, in different energies, which are reported by various collaborations, such as CDF, CMS, ATLAS, and LHCb. It is shown that the NLO-MRW and KMR schemes predict closer results to the data compared to the LO-MRW, since we do not have fragmentation. It is demonstrated that while the $q^{*}+{\overline{q}}^{*}\to {\gamma }^{*}/Z+g\to l^{+}+l^{-}+g$ subprocess has a negligible contribution, it has a sizable effect in the low dilepton transverse momentum. In agreement with the NNLO, perturbative quantum chromodynamics (pQCD), report (pythia, sherpa, etc.) by including the higher-order perturbative contributions the better results are archived. On the other hand as the scale of energy increases, for the LHC energies, the Compton subprocess, i.e., $q^{*}+g^{*}\to {\gamma }^{*}/Z\to l^{+}+l^{-}+q$, has the largest contribution to the differential cross section in the most intervals of some observables, as is expected. The variation of the differential cross section with respect to the various variables such as the invariant mass, the center of mass energy, etc. are discussed. In order to validate our results, we also consider the strong ordering constraint and the KaTie parton-level event generator.

We examine the feasibility of the Bell test (i.e., detecting a violation of the Bell inequality) with the ATLAS detector at the Large Hadron Collider (LHC) at CERN through the flavor entanglement between the $B$ mesons. After addressing the possible issues that arise associated with the experiment and how they may be treated based on an analogy with conventional Bell tests, we show in our simulation study that under realistic conditions (expected from the LHC Run 3 operation) that the Bell test is feasible under mild assumptions. The definitive factor for this promising result lies primarily in the fact that the ATLAS detector is capable of measuring the decay times of the $B$ mesons independently, which was not possible in the previous experiment with the Belle detector at KEK. This result suggests the possibility of the Bell test in much higher energy domains and may open up a new arena for experimental studies of quantum foundations.

The singlet Majoron model of seesaw neutrino mass is appended by one dark Majorana fermion singlet $\chi$ with $L=2$ and one dark complex scalar singlet $\zeta$ with $L=1$. This simple setup allows $\chi$ to obtain a small radiative mass anchored by the same heavy right-handed neutrinos, whereas the one-loop decay of the standard model Higgs boson to $\chi \chi +\overline{\chi }\overline{\chi }$ provides the freeze-in mechanism for $\chi$ to be the light dark matter of the Universe.

In the LHC searches for gluinos it is usually assumed that they decay predominantly into the lightest neutralino plus jets. In this work we perform a proof-of-concept collider analysis of a novel supersymmetric signal in which gluinos decay mostly into jets and the bino-like neutralino (${\tilde{\chi }}_3^0$), which in turn decays into the lightest Higgsino-like neutralino (${\tilde{\chi }}_1^0$), considered the dark matter candidate, together with the SM-like Higgs boson ($h$). This new physics signal then consists of an LHC final state made up by four light jets, four $b$-jets, and a large amount of missing transverse energy. We identify $t\overline{t}$, $V+\text{jets}$ ($V=W$, $Z$), and $t\overline{t}+X$ ($X=W$, $Z$, ${\gamma }^{*}$, $h$) productions as the most problematic backgrounds, and develop a search strategy for the high luminosity phase of the LHC, reaching signal significances at the evidence level for a luminosity of $1000{\mathrm{fb}}^{-1}$. The prospects for a luminosity of $3000{\mathrm{fb}}^{-1}$ are even more promising, with discovery-level significances.

$CPT$ invariance is one of the most fundamental symmetries in nature and it plays a major role in the formulation of quantum field theory. Although no definitive signal of $CPT$ violation has been observed so far, there are many reasons to carefully investigate various low-energy phenomena that can provide better probes to test $CPT$ symmetry. In this context, neutrino experiments are expected to provide more stringent bounds on $CPT$ invariance violation when compared to the existing bounds from the Kaon system. In this work, we investigate the sensitivity of the upcoming long-baseline experiments: Hyper-Kamiokande (T2HK, T2HKK), ESSnuSB, and DUNE to constrain the $CPT$ violating parameters $\mathrm{\Delta }({\delta }_{CP})$, $\mathrm{\Delta }(\mathrm{\Delta }{m}_{31}^2)$, and $\mathrm{\Delta }({\sin }^2{\theta }_{23})$, which characterize the difference between neutrino and antineutrino oscillation parameters. Further, we analyze neutrino and antineutrino data independently and constrain the oscillation parameters governing them by considering the combination of these experiments ($\mathrm{DUNE}+\mathrm{T}2\mathrm{HKK}$ and $\mathrm{DUNE}+\mathrm{ESSnuSB}$). In addition, assuming $CPT$ symmetry is violated in nature, we study the individual ability of the aforementioned experiments to establish $CPT$ violation. We found that the experiments Hyper-Kamiokande (T2HK, T2HKK) and ESSnuSB, along with DUNE, will be able to establish $CPT$ violation in their proposed run-times.

The production of charmonium associated with Higgs boson via gluon fusion has been investigated by Kniehl, Palisoc, and Zwirner [Phys. Rev. D 66, 114002 (2002)] in which they considered the contribution of the final Higgs boson radiation off the charm quark at tree level and found that this process is far too rare to be observable in any of the considered experiments. In this paper, the production of prompt $J/\psi$ associated with the Higgs boson via gluon fusion at the 14 TeV LHC within the factorization formalism of nonrelativistic quantum chromodynamics is revisited. After considering the contribution from the final Higgs boson radiation off the top quark in the loop, which is more than 3 orders of magnitudes higher than the charm quark at tree level, the production of prompt $J/\psi$ associated with the Higgs boson has great potential to be detected. The prompt $J/\psi$ production includes the direct production and indirect production via radiative or hadronic decays of high excited charmonium states. For the direct $J/\psi +H$ production via loop-induced gluon fusion, the ${{}^{3}S}_1^{(8)}$ Fock state gives the dominant contribution to the cross section, which is about 95% of the total direct production. The indirect loop-induced contribution is appreciable, since the summation of $\psi (2S)+H$, ${\chi }_{c1}+H$ and ${\chi }_{c2}+H$ is about 34% of the total cross section of prompt $J/\psi +H$. The indirect contribution from ${\chi }_{c0}+H$ is tiny and can be neglected. With great potential to be detected, prompt $J/\psi$ production associated with the Higgs boson can help us to further understand the mechanism of the color octet, as well as being useful to further investigate the coupling of the Higgs boson and fermions.

As a first step towards a realistic phenomenological description of vector and axial-vector mesons in nuclear matter, we calculate the spectral functions of the $\rho$ and the $a_1$ meson in a chiral baryon-meson model as a low-energy effective realization of QCD, taking into account the effects of fluctuations from scalar mesons, nucleons, and vector mesons within the functional renormalization group (FRG) approach. The phase diagram of the effective hadronic theory exhibits a nuclear liquid-gas phase transition as well as a chiral phase transition at a higher baryon-chemical potential. The in-medium $\rho$ and $a_1$ spectral functions are calculated by using the previously introduced analytically-continued FRG (aFRG) method. Our results show strong modifications of the spectral functions—in particular near the critical endpoints of both phase transitions—which may well be of relevance for electromagnetic rates in heavy-ion collisions or neutrino emissivities in neutron-star merger events.

Here we derive the relativistic resistive dissipative second-order magnetohydrodynamic evolution equations using the Boltzmann equation, thus extending our work from the previous paper [A. K. Panda et al., J. High Energy Phys. 03 (2021) 216] where we considered the nonresistive limit. We solve the Boltzmann equation for a system of particles and antiparticles using the relaxation time approximation and the Chapman-Enskog–like gradient expansion for the off-equilibrium distribution function, truncating beyond second order. In the first order, the bulk and shear stress are independent of the electromagnetic field, however, the diffusion current shows a dependence on the electric field. In the second order, the new transport coefficients that couple electromagnetic fields with the dissipative quantities appear, which are different from those obtained in the 14-moment approximation [G. S. Denicol et al., Phys. Rev. D 99, 056017 (2019).] in the presence of the electromagnetic field. Also, we found the various components of conductivity in this case.

We study the effects of addition of the Chern-Simons (CS) term in the minimal Yang-Mills (YM) matrix model composed of two $2\times 2$ matrices with $SU(2)$ gauge and $SO(2)$ global symmetry. We obtain the Hamiltonian of this system in appropriate coordinates and demonstrate that its dynamics is sensitive to the values of both the CS coupling, $\kappa$, and the conserved conjugate momentum, $p_{\varphi }$, associated to the $SO(2)$ symmetry. We examine the behavior of the emerging chaotic dynamics by computing the Lyapunov exponents and plotting the Poincaré sections as these two parameters are varied and, in particular, find that the largest Lyapunov exponents evaluated within a range of values of $\kappa$ are above what is computed at $\kappa =0$, for $\kappa p_{\varphi }<0$. We also give estimates of the critical exponents for the Lyapunov exponent as the system transits from the chaotic to nonchaotic phase with $p_{\varphi }$ approaching to a critical value.

We study notions of complexity for link complement states in Chern-Simons theory with compact gauge group $G$. Such states are obtained by the Euclidean path integral on the complement of $n$-component links inside a 3-manifold $M_3$. For the Abelian theory at level $k$ we find that a natural set of fundamental gates exists, and one can identify the complexity as differences of linking numbers modulo $k$. Such linking numbers can be viewed as coordinates which embeds all link complement states into ${\mathbb{Z}}_k^{\otimes n(n-1)/2}$, and the complexity is identified as the distance with respect to a particular norm. For non-Abelian Chern-Simons theories, the situation is much more complicated. We focus here on torus link states and show that the problem can be reduced to defining complexity for a single knot complement state. We suggest a systematic way to choose a set of minimal universal generators for single knot complement states and then evaluate the complexity using such generators. A detailed illustration is shown for $SU(2{)}_k$ Chern-Simons theory, and the results can be extended to a general compact gauge group.